Sarah Palin and her daughter Bristol have slammed Lena Dunham over her recent claims in her book she "sexually experimented" with her sister - claiming Josh Duggar, who has admitted to molesting younger girls, shouldn't have been treated worse than her.

19 kids and counting star Josh has admitted molesting children - including some of his younger sisters - on several occasions when he was 15, and has since apologised for the crimes.

But now Sarah and Bristol, while agreeing he did wrong, have defended the reality star - claiming he shouldn't have been treated any worse than Lena Dunham.

Lena recently appeared to admit "sexually experimenting" with her younger sister in her book Not That Kind of Girl, and the Palins both hit out at "liberal media" attacking the Duggars while Lena seems to get a "total pass".

Josh Duggar admitted to molesting younger girls (Image: Getty)

Bristol first wrote a blog post on Patheos, hitting out at "double standards", as she wrote: "I can't believe how crazy the media is going over the Duggar family compared to the big fat yawn they gave Lena Dunham when she wrote in her book that she sexually experimented with her sister."

She then included an alleged extract from the book, in which Lena appears to describe the experimentation with her sister - even saying she "would do anything a sexual predator might do".

Her mum Sarah praised her daughter in a lengthy Facebook post, before making her own views known in a lot more detail.

"The intolerant left's destructive personal intrusions and narrow-mindedness applied to their chosen targets are bad enough, but their double standards are beyond the pale," Sarah wrote.

She went on to make it clear she knows what Josh did was wrong, and he deserves punishment, but she believes so does Dunham.

Lena Dunham previously hit out at claims she molested her sister (Image: Getty)

"I'm not defending the Duggar boy's obvious wrongdoing over a decade ago. The main victim in any story like this isn't the perpetrator, it's the innocent ones so harmfully affected. I'm not an apologist for any sexual predator, but I'm sickened that the media gives their chosen ones a pass for any behavior as long as they share their leftwing politics," she added.

"Case in point, they suggest Lena Dunham's sexual assault on her sibling is cute, and she's rewarded for it with fame and fortune. Meanwhile, they crucify another, along with an entire family."

After her book sparked outrage at the time, Lena spoke out to explain the passage about her sister Grace.

"The right wing news story that I molested my little sister isn't just LOL—it's really f**king upsetting and disgusting," she wrote online.

"And by the way, if you were a little kid and never looked at another little kid's vagina, well, congrats to you. Usually this is stuff I can ignore but don't demean sufferers, don't twist my words, back the f**k up bros.

"I told a story about being a weird 7 year old. I bet you have some too, old men, that I'd rather not hear. And yes, this is a rage spiral. Sometimes I get so mad I burn right up. Also I wish my sister wasn't laughing so hard."